1. Setup¶
In [1]:
import numpy as np
import tensorflow as tf
import matplotlib.pyplot as plt
import keras
import scprep
import m_phate
import m_phate.train
import m_phate.data
Let's set the session so we can limit what percentage of the GPU is used, for courtesy's sake.
In [2]:
keras.backend.set_session(tf.Session(config=m_phate.train.build_config(limit_gpu_fraction=0.2)))
Now we load MNIST in preprocessed form.
In [3]:
x_train, x_test, y_train, y_test = m_phate.data.load_mnist()
2. Build the neural network¶
In [4]:
# leaky relu activation function
lrelu = keras.layers.LeakyReLU(alpha=0.1)
# input layer
inputs = keras.layers.Input(
shape=(x_train.shape[1],), dtype='float32', name='inputs')
# three dense hidden layers
h1 = keras.layers.Dense(64, name='h1')(inputs)
h2 = keras.layers.Dense(64, name='h2')(lrelu(h1))
h3 = keras.layers.Dense(64, name='h3')(lrelu(h2))
# output layer
outputs = keras.layers.Dense(
10, activation='softmax', name='output_all')((lrelu(h3)))
Wow, that was easy.
3. Set up the neural network trace¶
Here we randomly select ten examples of every digit from the test set - the hidden activations of these images will form our data tensor to be visualized.
In [5]:
np.random.seed(42)
# select the digit indices in the test set
trace_idx = []
for i in range(10):
trace_idx.append(np.random.choice(np.argwhere(
y_test[:, i] == 1).flatten(), 10, replace=False))
trace_idx = np.concatenate(trace_idx)
# extract the selected images
trace_data = x_test[trace_idx]
# build a keras model which outputs the hidden activations
model_trace = keras.models.Model(inputs=inputs, outputs=[h1, h2, h3])
# use the TraceHistory helper class to store the outputs at each epoch
trace = m_phate.train.TraceHistory(trace_data, model_trace)
4. Train the network¶
In [6]:
# create another callback to store loss, accuracy etc
history = keras.callbacks.History()
# compile the model
optimizer = keras.optimizers.Adam(lr=1e-5)
model = keras.models.Model(inputs=inputs, outputs=outputs)
model.compile(optimizer=optimizer, loss='categorical_crossentropy',
metrics=['categorical_accuracy', 'categorical_crossentropy'])
# train!
model.fit(x_train, y_train,
batch_size=128, epochs=200,
verbose=0, callbacks=[trace, history],
validation_data=(x_test,
y_test))
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5. Retrieve the output¶
There are a lot of metadata features we might be interested in visualizing, so we show you all of them here.
The most important element here is the first: the n_epochs x n_neurons x n_examples tensor. We often refer to the flattened tensor as this is what will be returned by M-PHATE: this is the n_epochs*n_neurons x n_dim matrix to be visualized.
In [8]:
# the actual data tensor
trace_data = np.array(trace.trace)
n_epochs = trace_data.shape[0]
n_neurons = trace_data.shape[1]
# the train loss for each element of the flattened trace
loss = np.repeat(history.history['categorical_crossentropy'], n_neurons)
# the validation loss for each element of the flattened trace
val_loss = np.repeat(history.history['val_categorical_crossentropy'], n_neurons)
# the train accuracy for each element of the flattened trace
accuracy = np.repeat(history.history['categorical_accuracy'], n_neurons)
# the validation accuracy for each element of the flattened trace
val_accuracy = np.repeat(history.history['val_categorical_accuracy'], n_neurons)
# the unique neuron id for each element of the flattened trace
neuron_ids = np.tile(np.arange(n_neurons), n_epochs)
# the hidden layer that each element of the flattened trace belongs to
layer_ids = np.tile(np.concatenate([np.repeat(i, int(layer.shape[1]))
for i, layer in enumerate(model_trace.outputs)]),
n_epochs)
# the current epoch for each element of the flattened trace
epoch = np.repeat(np.arange(n_epochs), n_neurons)
# the label of each digit we selected: this should be the same as `np.repeat(np.arange(10), 10)`
digit_ids = y_test.argmax(1)[trace_idx]
# the average activity over digit labels for each element of the flattened trace
digit_activity = np.array([np.sum(np.abs(trace_data[:, :, digit_ids == digit]), axis=2)
for digit in np.unique(digit_ids)])
# the digit label with the highest average activity for each element of the flattened trace
most_active_digit = np.argmax(digit_activity, axis=0).flatten()
6. Visualize the data tensor¶
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# calculate M-PHATE
m_phate_op = m_phate.M_PHATE()
m_phate_data = m_phate_op.fit_transform(trace_data)
# plot the results
plt.rc('font', size=14)
fig, (ax1, ax2, ax3) = plt.subplots(
1, 3, figsize=(18, 6), sharex='all', sharey='all')
scprep.plot.scatter2d(m_phate_data, c=epoch, ax=ax1, ticks=False,
title='Epoch', label_prefix="M-PHATE")
scprep.plot.scatter2d(m_phate_data, c=layer_ids, ax=ax2, title='Layer',
ticks=False, label_prefix="M-PHATE")
scprep.plot.scatter2d(m_phate_data, c=most_active_digit, ax=ax3,
title='Most active digit',
ticks=False, label_prefix="M-PHATE")
plt.tight_layout()
In [10]:
# do it in 3D!
m_phate_op.set_params(n_components=3)
m_phate_data = m_phate_op.transform()
# plot the results
scprep.plot.rotate_scatter3d(m_phate_data, c=most_active_digit,
title='Most active digit',
ticks=False, label_prefix="M-PHATE")
Out[10]: